Situation of Phytophthora lateralis in France
In France, Phytophthora lateralis (EPPO A1 List) had been isolated from Chamaecyparis lawsoniana on two occasions (in 1996 and in 1998). The origin of these detections could not be fully traced-back (it can be recalled that imports of C. lawsoniana from third countries are prohibited in the European Union). The disease was no longer reported until 2005 when tree mortality and symptoms resembling those of P. lateralis were observed on several hedges of C. lawsoniana in Finistère department (Bretagne region, Western France). In Bretagne, C. lawsoniana trees were planted during the 1970s as windbreaks after removal of the traditional hedgerows (i.e. during the transformation of the historical low-intensity farming system into a more intensive one). Several samples were collected and tested but P. lateralis could not be detected. Positive results confirming the presence of P. lateralis were obtained in 2009 in soil and in root samples of C. lawsoniana collected from 4 distantly separated municipalities in Finistère (Landrévarzec, Lopérec, Moëlan, Scaër). Although the presence of the pathogen was only confirmed in these 4 localities, it is noted that the disease has already had a serious impact on the landscape causing decline and mortality of several thousands of Chamaecyparis trees over an area covering approximately 400 km².
In Bretagne region, in addition to typical symptoms of P. lateralis (i.e. discoloration and decline of the whole canopy associated with root and collar necrosis) the presence of unusual symptoms was also noted. In two sites, dead branches with necrotic lesions were observed. The decline was localized in the middle or lower part of the canopy and seemed to be progressively spreading from the foliage towards the trunk. This type of decline could not be associated with any root or collar lesions. The observation of these aerial infections without root infections suggest that in addition to dissemination by water, soil and plants, P. lateralis might be air-dispersed (as in the case for P. ramorum).
The situation of Phytophthora lateralis in France can be described as follows: Present, occurs in Bretagne region (Finistère) on Chamaecyparis lawsoniana trees planted as windbreaks, under official control.
NPPO of France (2010-12).
Piou D, Robin C (2010) Rapport sur la détection de Phytophthora lateralis en Bretagne (Finistère). INRA. Ministère de l’Alimentation de l’Agriculture et de la Pêche, 14 pp.
Robin C, Piou D, Feau N, Douzon G, Schenck N, Hansen EM (2011) Root and aerial infections of Chamaecyparis lawsoniana by Phytophthora lateralis: a new threat for European countries. Forest Pathology (in press).
Article first published online: doi: 10.1111/j.1439-0329.2010.00688.x